The Potato Underground — Discover the Goodness of America's Favorite Vegetable

By Kathie Beals

This past August I had the opportunity to speak at the annual Potato Association of America (PAA) meeting held in Idaho Falls, ID. Before describing the meeting itself, I think a bit of background about the PAA is in order. The PAA was formed in 1913 and serves as the official professional society for those involved in potato research, extension, production, and utilization. The association provides opportunities to contribute in one or more of eight sections: Breeding & Genetics, Certification, Extension, Plant Protection, Physiology, Production & Management, and Utilization & Marketing.

The annual meeting features research presentations, demonstrations and workshops encompassing a range of topics related to potatoes including nutrition, plant protection, breeding and genetics, physiology as well as industry topics including marketing, production and management. My presentation was part of the opening Keynote Symposium which was entitled, “Enhancing the Nutritional Value of Potato Tubers.” As the opening presentation, it was my responsibility to “set the stage” for the rest of the Symposium. Thus, I began with a historical perspective of the important role that potatoes have played nourishing mankind for centuries. I then focused on the nutrient content of potatoes, including carbohydrate, protein, vitamins and minerals. For example, potatoes are now being recognized for their resistant starch content. Current research is investigating the physiological functions, health benefits and ways to maximize dietary resistant starch. In addition to carbohydrates, potatoes contain a small but significant amount of protein, comparing favorably and even exceeding that of many other common vegetables. Moreover, their unique amino acid profile makes potatoes a perfect protein complement to many other vegetable and grain sources. In addition, potatoes are an excellent source of Vitamin C and rank highest for potassium among the top 20 most frequently consumed raw vegetables and the 20 top most frequently consumed raw fruits.

I finished my presentation by addressing some of the more common myths and misconceptions surrounding potatoes including:

1. “Potatoes are fattening”- In fact, a medium potato has just 110 calories and no fat. No single food causes excess weight gain; rather, gaining weight is a function of consuming more calories than you expend (1).
2. “Potatoes have a high glycemic index (GI)”- In fact, the GI of potatoes vary significantly depending upon the variety, origin, and cooking methods used (2, 3). For example, the GI of Russet potatoes range from 56 -111 depending on the country in which they were grown (4). Similarly a cooked red potato eaten hot has been shown to have a GI of 88 while eating that same potato cold lowers the GI to 56 (2).
3. “Potatoes are not satiating”- In fact a study conducted by Holt and colleagues and published in the European Journal of Clinical Nutrition showed that, out of 38 commonly consumed foods, potatoes were the most satiating (5).
4. “All of the nutrients in potatoes are found in the skin”- In fact, the only nutrient that is lost appreciably when the skin is removed is fiber. About ½ of the fiber is found in the skin, while the bulk of the other nutrients (carbohydrate, protein, vitamins and minerals) are found in the flesh (USDA SR 18). Nonetheless, it is recommended that potatoes be eaten with the skin to maximize the nutrient consumption.

References

1. FDA/CFSAN. Calories Count- Report from the Working Group on Obesity. March 12, 2004 http://www.cfsan.fda.gov/~dms/owg-toc.html accessed 11-19-07.
2. Pi-Sunyer, FX. Glycemic index and disease. Am J Clin Nutr. 2002; 76(suppl):290S-298S
3. Fernandes G, Velangi A, Wolever TMS. Glycemic index of potatoes commonly consumed in North America. J Am Diet Assoc. 2005;105:557-562.
4. Foster-Powell K, Holt SHA, Brand-Miller JC. International table glycemic index and glycemic load: 2002. Am J Clin Nutr. 2002;76:5-56.
5. Holt SHA, et al. A satiety index of common foods. Eur J Clin Nutr. 1995;49:675-690.
6. U.S. Department of Agriculture, Agricultural Research Service. 2005. USDA National Nutrient Database for Standard Reference, Release 18. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp

By Katherine Beals, Ph.D., R.D., F.A.C.S.M.

I am Dr. Katherine Beals, R.D., and I have served as the nutrition consultant to the United States Potato Board for almost three years now.  In this capacity I direct the basic research program and monitor nutrition issues that are related, directly or indirectly to potatoes.  One of the most controversial nutritional issues involving potatoes is their relationship with diabetes.  Potatoes have been frequently (and perhaps unjustly) accused of raising blood glucose levels, exacerbating or even causing diabetes, and thus are recommended to be limited or even removed from the diets of those suffering from or at risk for diabetes.  However, a recent study published in the American Journal of Epidemiology found that potato consumption was not associated with an increased risk of developing type 2 diabetes. 

Specifically, researchers from the University of Melbourne and the Cancer Council, Victoria investigated the association between a variety of dietary patterns and type 2 diabetes in a 4-year prospective study of 36,787 adults.   The results indicated that a dietary pattern characterized by meats and fatty foods was associated with increased diabetes risk while a dietary pattern characterized by a variety of salad and cooked vegetables, including potatoes cooked in healthful ways, was associated with a decreased risk.  Interestingly, when vegetables as a group (excluding potatoes) were examined independently the association with decreased diabetes risk disappeared.  

Tufts University Research Shows Calories More Important than Glycemic Load

Another common nutrition misconception that continues to plague potatoes is that they are fattening.  This stems from the notion that they are high in calories, high on the glycemic index and leave you feeling unsatisfied (i.e., not satiating).  In fact, a medium potato (5.3 oz), with skin, has 110 calories, no fat, no sodium, and no cholesterol.  Moreover, researchers from  the Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University recently published evidence suggesting that when it comes to weight loss the glycemic load of the diet doesn’t matter as long as calories are reduced and fiber intakes are sufficiently high.  In this study, 34 overweight, but otherwise healthy, men and women achieved and maintained similar weight and body fat losses after one year, whether they were on a low-glycemic-load or a high-glycemic-load diet. 

Potatoes Fill You Up, Not Out

And, far from leaving you feeling hungry and unsatisfied, potatoes have actually been shown in research studies to be one of the most satiating foods around.  In a study published in 1995 in the American Journal of Clinical Nutrition Australian researchers examined the satiety value of 240 calorie portions of 38 different foods representing all the basic food groups.  Subjects consumed the foods in random order and rated them based on the degree of fullness they provided. Fruits and vegetables were at the top of the satiety index (SI) list of foods. In fact, the highest SI score was produced by potatoes, which was more than three times the SI of white bread!

Potatoes definitely fit within a nutrient dense diet. They are a good source of potassium, provide almost ½  your daily requirement for vitamin C and are a good source of B vitamins (particularly vitamin B6). You can see the values right on the FDA nutrition facts label. One of the things I love most about them is their versatility (i.e., they can be prepared in so many different ways) and they provide a great accompaniment to many other foods, particularly vegetables.  In fact, my favorite potato recipe is a baked potato topped with broccoli and melted cheese. 

Check back soon to learn more about potato nutrition.  I’ll be posting information regularly.  If you have a potato-related nutrition question for me, please contact me.